Electronic devices are often constructed of two pieces, the two pieces being moveable between an open position and a closed position with respect to each other. It is sometimes desirable to operate the electronic device in a different mode of operation when the two pieces are in the closed position. An example of such a device is a folding portable radiotelephone, also known as a clamshell phone or flip phone. The two-piece folding design, which has a first piece and second piece connected by a hinge, allows the portable radiotelephone to be compact and, when closed, the second piece provides protection for the keyboard and the display screen.
Other radiotelephones use a sliding second piece that provides similar functionality.
When the second piece is closed, the radiotelephone may be switched to a ‘standby’ mode of operation, in which the screen and other energy consuming operations are deactivated to conserve battery power, or switched off. Conventionally, a mechanical switch on the hinge is used to detect whether the second piece is open or closed. More recently, a Hall Effect sensor has been used to detect when the second piece is closed. However, mechanical switches are subject to failure after prolonged use and Hall Effect sensors, which use a magnetic field, may interfere with the radio of the radiotelephone.
Other electronic devices, such as PDA's and portable computers, also incorporate hinged, sliding or removable second pieces. It is also desirable to operate these devices in different modes depending upon whether the second piece is open or closed